Gear-cutting machine.



l. E. IVICCRACKEN.

GEAR CUTTING MACHINE. APPLICATION FILED DEC.8.1913.

Patentedsept. 12,1916.

2 SHEETSSHEET I.

l. E. MCCRACKEN.

GEAR CUTTING MACHINE.

APPLICATION FILED 050.8. ms.

'2 SHEETS-SHEET 2.

Patented Sept. 12, 1916.

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master rack operating mechanism; Fig. is

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- herring bone type,

GEAR-CUTTING MACHINE.

To all whom it may concern."

Be it known that l, a resident of Pittsburgh, in the county of Allegheny, and State invented a. new and useful Improvement in Gear-Cutting Machines, of which the following is a specification.

This invention relates to apparatus for cutting gears or pinions, and particularly gears or pinions having-teeth of modified that is, where the teeth are curved or deviate circumferentially of thegear from end to end from a line parallel with the gear axis. x

The invention has particular relation to a machine for carrying out the method and producing the article described in my prior application for method of cutting gears,

filed April 4, 1913, Serial No. 758,967.

One object of the invention is to produce a simple machine for carrying out the method of my prior application above identit ed, and which produces a mathematically correct gearvby A further object of the invention is to provide a gear cutting machine for cutting curved-tooth gears of any desired form, that is, in which the teeth may have an de gree of curvature, irrespective of-the iameter of the gear, and, Within limits, irre spective of the width of the gear face.

A further object of the invention is to provide agear cutting machine which is rapid in operatiomin which the cutter can not damage the partially formed tooth,and which is entirely automatic in operation.

A further object of the invention is to provide a gear cutting machineof the character described embodyingautomatic mechanism for traversing the table and for indexing the gear blank cutting operations.

Further objects of the invention part obvious and in are in in detail hereinafter.

In the drawings, Figure 1 is a side elevation, partly in section, of one form of ma chine'embodying the invention; Fig. 2 is an end view of the-same; Fig. 3 is a sectional plan view on-the line 33, Fig. 1; Fig.- is'a detail elevation, showing the in art a side elevation and impart a longitu inal sectional view on the line 5-5, Fig, hrough the cutterhead; Fig. 6 is a front ISAAC E. MCCRACKEN,

of Pennsylvania, have a. true generating operation.

between successive part will appear more teeth may be generated on Specification of Letters Patent. Patgntgqfl @rgplo 1%, 1191m Application filed December 8, 1913. Serial No.

vided with the usual cone pulley or other driving device 4%. Spindle 3 projects over a work carrying bed 5 which is preferably Hlj-l1ttl0l8 vertically on the frame 1 in the usual manner. Said bed is rovided on its upper'face with longitudina ways, extend ing in a direction parallel with the axis of the spindle 3, along which is movable a Work carriage 6. 'S'aid carriage may be moved along its wc ys by any suitable means, such as by a feed screw 7.' Carriage 6 is provided on its upper face with guides 8 extending ina direction normal spindle. 3 and along or support 9. Saidtable-or support 9 may be moved or traversed along the ways 8 in any suitable manner, such as by a feed screw 10 journaled in the carriage 6 and 00- operating with the nut 11 on the table 9. Said feed screw maybe operated, such as by gears 13 driven by an operating shaft 14, which may be rotated in dill dli

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to the axis of the which is movable a tableoperated by a hand wheel 12, but preterably is automatically one thereof to the shaft. Preferably, suitable mechanism is provided for shifting the "clutch 17 at a predetermined point in the table 9 in each direction, so,

travel of the that the driving mechanism automatically traverses the table back .LIld forth over a path of predetermined length. In the form shown this mechanism comprises a-clutch operating lever 17 fulcrumed on the carriage 6 and arranged to be contacted by two Stops 17 udjustably mounted on the table 9 in any suitable manner so they maybe shifted to various positions alongflthe hne of movement of the table. The particular form of the carriage reversing mechanism is, however, not essential, and no further description thereof is necessary. v

It is well known that straight involute an ordinary gear or pinion by rolling the blank paste re- Mill.

eiprocating cutter. havinga cutting tooth or teeth shaped to correspondwith the teeth of the normal rack, in'a. direction normal to the direction of reciprocation of the cutter and in'the plane of the rack. The present machine is designed teeth, so that theeutter, eating in a straight line, path in a plane,

to generate curved instead of recipromovesin a curved and is illustrated as rotating about the axis of spindle 3. A rolling motion is produced between the blank and cutter along or on the plane of curved path of movement of the cutter, and in the present machine the blank is rolled along or on a plane transverse to' he axis of rotation of the-cutter and tangent to the pitch line of the gear to be cut.

Any suitable arrangement of mechanism may be provided for producing the relative rolling motion between the blank and'the cutter. As illustrated, table'9 carries a fixe or non-rotatable arbor 18 on which is rotatably mounted a bushing 19 which supportsin fixed relation with each other a master gear 20, a

ratchet 35 and the blank A to be cut, these three members being spaced apart by short bushings 19 and being all keyed to and rotatable wi 11 the bushing 19;- The master gear 20 has the same number of teeth responding to various sizes of the support 22 and rest loosely on ledges or shelves 25 on said members 24. Eachmaster gear 20 has a mating "master rack 21, and t e teeth of each pair are preferably beveled or chamfered at their ends, as shown at 21, Fig. 7, for a purpose to be described.

Suitable means is provided for, indexing the blank A one step at the conclusionlof each cutting operation.

the bed 5 carries two pillars or supports 26'to each of which s pivoted a lever 27.. -Said levers have their adjoining 'end por tions slotted to receive a pin 28 connecting them to' a lifting member'29, which is slidably mounted in a support 30 on the bed and at its up er end has a wide fiat head 29 engagingt ,pro ecting-en'd 29 let into a socket in the rack. The movable table 9' is provided with a longitudinalT-slot 31 in .which are ad justab y mounted two cams 32, having beveled fa'ces33 arranged to contact arms'on the ends of the levers 'stop +12 strikes lever 1 suitable spr ing device,

shown in Fig;

21, the

The

. the cam 33 In the form shown e under surface of rack 21 and a i to the spindle 3 with 27 .and oscillate them 66 aboutthe1r pivots, thereby raising the rack 21 entirely ter gear 20. are secured in the slots 31 in such positions as to contact their respective levers after the blank has rolled completely across the cutting-range of the cutting tool.

The indexing movement occurs ust afterthe rack 21 and gear-20 have been wholly disengaged n the manner just described. It is produced, in the machirie-shown, by either of two spring pressed pawls 34 arranged during the 'last' part of the carriage movement in either direction to engage and r0- tate the ratchet 35. Each of said pawls is mounted on a carrier 36 adjustable along a swinging bar 37 so it-1nay be located ina position to engage the ratchet at the proper time. One end of bar 37. is pivoted'to an arm 38 fulcrumed on the support 22,- while its other end is pivotally connected to a lever 39 fulerumed at 40 to an arm 11 mgidly connected tothe support 22. Two steps -12, 43, longitudinally adjustable in slots in the table 9 produce the indexing movement. When the carriage moves'in' one direction 39 and moves the bar 3. When the carriage other direction stop 43-strikes 37 to the-left in Fig. moves in the out of'engagement with the mas The cams 32am adjusted and- .lever 38 near.its-fulcrum and swings its outer end to the left in Fig. 3 and in advanceof the carriage, said lever and the bar 37 being returned to normal position by any such as the spring 65 3, and which connects the bar 37 to lever 39. Said spring is stretched each' time the bar 37 moves to the left. At

each of these times one of the pawls 34 is in contact with the ratchet 35 and the mechanism is so proportioned that before the carriage movement is reversed. the blank is indexed approximately one tooth. The blank is accuratelyindexed or positioned on the backward movement of the carriage, when moves away fronrthe lever 27 and allows the rack 21 to drop. The chamfered ends of the'teeth of rack 21 and gear 20 allow for slight varlation in'the indexing movement produced by the rack 21 is prefera ly heavy. enough so that in dropping into engagement its teeth act as wedges to rotate the blank into final accurately indexed position.

As described in my I above identified, the gear teeth are generated by two cutters, .one of which forms the convex sidesof the teeth and the other the con- "thc pawls 34, and

prior application cave sides thereofi. .Each of these cutters may be'a single tooth cutter fixedly secured. its generating cutting edgeat'the proper distance from the-axis thereof, oreach cutter may be in the form of a ,hollow' milling cutter as vdescribed in said application. 'Pre rably; however, a special form of cutter head is used, wherein Y the cutter or'cuttersmay be held in proper 1 cutting relation to the blank when moving across its face in one direction and may be withdrawn from cutting relation with the blank when passing across the same in the other direction. This prevents any liability of the cutters injuring the blank or a partially formed tooth thereof during the backter carrying arm ward sweep of the cutter, and also enables the blank to be traversed entirely across the cutting head, and produces a tooth of any desired degreeof curvature irrespective of the diameter of the blank or the width of its facr. Any suitable form of cutting head which produces these results may be used, but in the form shown in the drawings the cutting head comprises a disk or plate 44 threaded or otherwise rigidly secured to the rotatable spindle 3 and provided with a socket or seat 45 in its front face, from which extend a plurality of radially disposed slots or openings 46, five being shown. VVithinthe socket 45 is located a spider 47 rigidly held therein by a plate 48 screwed to the plate 44, said spider beingpr'ovided with a plurality of circumferentially spaced pairs of ears or lugs 49, one pair thereof lying in each of the radial slots 46. Between each pair of ears or lugs 49 is pivoted a outi 50, having a longitudinal seat 51 in its front face to receive the base of the cutter 52. Said cutters may be rigidly clamped in the seats 51 by any suitable means, such as by set screws 52 and may be adjusted to any radial position in said arms. The upright portion of the base or frame 1 has rig-idly secured thereto an annular cam 53, which surrounds the spindle 3. Each arm has pivotally connected to its outer end a cutter moving member, shown as a link 54, which is notchedor socketed at its rear end to embrace the periphery of cam 53. Each link is preferably provided with an anti-friction member, shown as a ball 55, which takes the thrus 'of the cam and decreases the friction. The bottoms of the radial slots 46 are inclined, so that the levers 50 have considerable movement there in.v Cam 53 is shaped to provide two plain portions, marked respectively 56 and 57, which lie in different planes normal to the spindle axis. These two portions of the cam are connected by inclined cam parts 58.! In operation the members 54 travel around the periphery of the cam 53 and are moved back and forth thereby in a di-rectionlengthwise of the spindle axis, the cutters being successively moved into and out of cutting relation with the blank.- Portion 56 of the cam holds the cutters in fixed cutting relation with the blank while they travel across its face in one direction. .Cam portion 57 holds the cutters out of cutting relation with the blankwhile they travel across its face in the other direction, and inclined cam parts 58 move the cutters back and forth between one of the pulleys 15 gage with the work tooth is entire blank and these two positions. members 54 may be held in engagement with the cam by any suitable means, such as by a ring 59 secured to the frame and surrounding said members.

In use of the machine a master gear 20 is chosen having a pitch diameter and number of teeth corresponding to the gear to be cut, and a master rack is selected to correspond with said gear. [The blank is rigidly secured to the bushing 19 and the cams 32 are secured in the proper adjusted positions on the table 9. A set of cutters 52 arranged to out either the concave or convex sides of the teeth is secured in the pivoted arms 50 at the proper distance from the axis of spindle 3. The machine is started by throwing clutch 1.7 into engagement with or 16 to move the table 9 in one direction along its ways, such as from left to right in Fig. 2. The blank rolls across the rotating cutters which enand generate one side face of a tooth. These cutters cross the face of the blank twice during each rotation around the axis'of spindle 3, but are only in cutting relation with the blank in cross ing the same in one direction, being with- The cutter moving When the cutter head,

blank has rolled clear across the a cam 82 lifts the rack 21 out of engagement with the gear 20 and one of the pawls 34 indexes 'the blank approximately one tooth. Clutch 17 is then thrown by a stop l7 into engagement with the other driving pulley and the carriage movement is reversed. WVhen the cam 32 moves out of engagement with its lever the rack 21 drops into engagement with gear 20 and the bushing 19 is rotated slightly to bring the blank into accurately indexed The blank then makes a return across the cutters and the face of traverse the next generated, the machine cutting as effectively when the blank rolls in one direction as when it rolls in the other. At the end of the return movement cf the carriage the other cam.32 disengages the rack and gear and the blank is indexed a second step by the second pawl 34, in the manner before described.

Successive operations proceed around the then the first set of cutters is removed and a second set of cutters for forming the other face of the teeth is substituted therefor. The blank is then rotatably adjusted about its axis and with an erence to the master gear and ratchet a disposition.

tance equal to one-half the circular pitch. 1

Successive cutting operations are then per-v finishing the gear.

It is to be understood that the invention set, thereby -motions between the which occur in is not limited to the particular form of machine shown in the drawings, which is merely illustrative of one embodiment of the invention, except as required by the scope of the appended claims.

blank and cutter which are essential and not the absolute motions the particular machine described.

. head avoids the gaging said rack and carrying a .rying traverse the blank past the cutter and carrymatic means The machine described is simple and produces all of the necessary motions for generating curved teeth with mathematically correct lines. It may be operated entirely automatically and produces gears at a high speed and consequently at low cost. Moreover, the particular arrangement of cutter liability of damaging the blank or any partially formed teeth thereof and permits the formation of teeth having any degree of curvature irrespective of the (iiiameter of the blank or the width of its ace.

What I claim is: r 1. A gear cutting machine, comprising a support, a cutter carrying spindle journaled therein, a blank carrying member movable on said support to traverse the blank past the cutter, rack and gear connec- -tions between said blankcarrying member and support for rotating the blank as it travels past the cutter, and means for disengear connections after the blank has moved beyond the cutter.

2. A gear cutting machine-,comprising a support, a spindle rotatable therein and cutter eccentr-1cally mounted thereon, a rack on said support, a blank carrying member movable on said support to traverse theblank past the cutter and carrying a gear rolling along sa'd rack, and means arranged to disengage t e rack and gear and index the blank at the conclusion of the cutting operation.

3. A gear cutting machine, comprising a support, a spindle rotatable therein and carrying a cutter eccentrically mounted thereon, a rack on said support, a blank earmember movable on said support to ing a gear rolling along said rack, and auto controlled by the carriage movement for disengaging said rack and gear and indexing the blank 4. A gear cutting machine, cutter, a blank carry'ng member, meansfor moving said cutter in a curved path in a It is the relative I pivoted tool support and tively comprising a meson plane tangent to the pitch line of the blank, means for producing relative rolling motion between said cutter and blank on said plane, and means for moving the cutter toward and-from the blank during the rolling motion.

5. A gear cutting machine, comprising a cutter, a blank carrying member, means for moving said cutter in a curved path in a plane tangent to the pitch lineof the blank, means for producing relative rolling motion between said cutter and blank on said plane, and means for holding the cutter in fixed cutting relation with the blank when traveling across the same in one direction and out of cutting relation therewith when traveling across the same in the other direction.

6. In a gear cutting machine, in combination, means for supporting the blank, a pivoted tool support, and tool thereon arranged to move in a path concentric to the axis of the support, adjusting means for varying the radial position of the tool relatively to the support pivot, and means for moving the tool support on its pivot to efiect the cut in the blank.

7. In a gear cutting machine, in combination, means for supporting the blank, a pivoted tool support and tool thereon arranged to move in a path concentric to the axis of the support, adjusting means for varying the radial position of the tool relatively to the support pivot, adjusting means for varying pivot relatively to the blank, moving the tool support on its pivot ,to eficct the cut in the blank.

8. In a gear cutting machine, in combination, means for supporting the blank, a

tool thereon arranged to move in a path concentric to the axis of the support, adjusting means for varying the radial position of the tool relato the support pivot, means for adjusting the support pivot toward and away from the axis of the blank, and means for moving the tool support on its pivot to eliect the cut in the blank.

In testimony whereof, I have hereunto set my hand. I

ISAAC n. M0CRAGKEN.-

.Witnesses:

GLENN H. LERESCHE,

WILLIAM B. WHARTON.

the position of the support and means for 

